Continental Drift and Plate Tectonics

Continental Drift Continental Drift and Plate Tectonicsand Plate Tectonics

Alfred WegenerAlfred Wegener1880-19301880-1930

● German scientist● Introduced the Theory of

Continental Drift in his book The Origin of the Continents and Oceans (1915)

● Many scientists had noticed the remarkable fit of the coastlines of South America & Africa ● First to use geological and

paleontological evidence to show these continents were once joined

Evidence of PangaeaEvidence of Pangaea

Theory of Continental DriftTheory of Continental Drift

• Proposed by Wegener in 1915• Used evidence from climate, fossils and

landforms to match up the continents• All of the continents were once joined in one

large supercontinent called Pangaea and have since drifted apart

• Wegener did not have a force to provide the movement so it was not accepted until the 1950’s● Wegener spent much of his life defending his theory

Wegener’s Continental DriftWegener’s Continental Drifthttp://www.ucmp.berkeley.edu/geology/anim1.html

225 million years ago all 225 million years ago all continents connected in continents connected in one land mass called one land mass called

PangaeaPangaea

180-200 million years 180-200 million years ago Pangaea separated ago Pangaea separated

into Laurasia and into Laurasia and GondwanalandGondwanaland

135 million years ago 135 million years ago Laurasia and Laurasia and

Gondwanaland began to Gondwanaland began to separate into continentsseparate into continents

65 million years ago the 65 million years ago the continents move even continents move even

further apartfurther apart

The position of the The position of the continents on Earth continents on Earth

todaytoday

Untold Untold Tragedies of Tragedies of Continental Continental

Drift Drift

The CrustThe Crust

• This is where we live!

• The Earth’s crust is made of:

Continental Crust

- thick (10-70km)- buoyant (less dense than oceanic crust) - mostly old - granite

Oceanic Crust

- thin (~7 km)- dense (sinks under continental crust)- Young - basalt

Earth’s InteriorEarth’s Interior• Lithosphere: Area

of the crust and the upper mantle.– Crust:

• Outer most layer• Continental crust

(less dense granitic)

• Oceanic crust (more dense basaltic)

• Asthenosphere:– Rocks are at or near

melting point– Exhibits plasticity – a

solid that flows like a liquid

AssignmentAssignmentIn your spiral – draw and color a picture of the Earth’s

interior, labeling the following:

Wegener’s Puzzling EvidenceWegener’s Puzzling Evidence1. Label the land masses on each sheet. Color the

fossil areas to match the legend below.

2. Cut out each of the continents along the edge of the continental shelf (the outermost dark line). Alfred Wegener's evidence for continental drift is shown on the cut-outs. Wegener used this evidence to reconstruct the positions of the continents relative to each other in the distant past.

3.Try to logically piece the continents together so that they form a giant supercontinent.

Africa

S. America

Australia

India

Antarctica

Plate TectonicsPlate Tectonics• Proposed in 1960’s by a variety of scientists

including Hess, Dietz and Vine• Suggests that the lithosphere is broken up into

many plates which are moving around the earth in different directions

• All of the continents were once together in one supercontinent – Pangaea

• Movement is caused by convection currents in the mantle of the Earth

• Explained the cause of earthquakes, volcanoes, mountain building

Plate TectonicsPlate Tectonics

• Plate Tectonics: Theory that the Earth’s lithosphere is broken into plates and float on the asthenosphere

• Convection Currents: Drives plate motion – hot magma rises from core, cools and sinks back to core – cycle starts over (think of a lava lamp)

Double BubbleDouble Bubble

• Make a double bubble map of Continental Drift and Plate Tectonics

CONCLUSIONCONCLUSION

• Imagine you are Alfred Wegener in 1915. Write a Claim – Evidence – Reasoning about your theory of Continental Drift.

• Use the evidence from the lab we just completed. Your reasoning you can come up with on your own (Remember it is 1915 and you are Wegener)

CER Peer EditingCER Peer Editing• Claim – All continents were once joined together and

have since drifted apart = 20pts

Is it a complete logical sentence = 10pts

• Evidence – Must mention at least 2 of the following:

Dinosaur Fossils, Plant Fossils,

Landforms (the way they fit together) = 30 pts

Is it a complete sentence? = 10pts

• Reasoning – Does it make sense? = 20 pts

Is it a complete sentence? = 10pts

Write the totals in the box at the bottom of the page